1. Field of the Invention
The present invention generally relates to a vacuum-processing apparatus and, in particular, to a vacuum-processing apparatus with an auto-calibration for an output of a pressure gage.
2 Description of the Related Art
In the process of manufacturing a semiconductor device, various types of well-known vacuum-processing apparatuses are used.
For example, a plasma etching apparatus is developed as one of the apparatuses that execute the dry etching technique for performing ultra micropatterning so as to satisfy the recent demand for high-density packaging and high integration. That is, the plasma etching apparatus utilizes a technique for producing a volatile material by causing ions or molecules in a plasma, which is generated by discharge in a processing chamber set at a low vacuum by introducing a predetermined gas, to react with a material to be etched.
In various types of vacuum-processing apparatuses such as a plasma etching apparatus, for example, to control the vacuum degree of the processing chamber at a predetermined value is an important factor that significantly influences the yield of the product. In this case, a pressure gage used for detecting the pressure, i.e., the vacuum degree of the processing chamber must have an anticorrosion property against a gas and the like subjected to reactions in the processing chamber and must be able to constantly detect an accurate vacuum degree.
For this purpose, for example, a pressure gage called a capacitance manometer which has an anticorrosion property is used in order to detect the pressure in the processing chamber and to control the detected vacuum state.
A conventional vacuum-processing apparatus uses such a pressure gage to detect the pressure state in the processing chamber as a voltage signal and to control and drive a pump and the like which performs vacuum suction of the interior of the processing chamber based on an output signal.
However, in the pressure gage of this type, its output value largely varies from time to time. Therefore, calibration of the pressure gage output must be performed at least once a day to perform zero point adjustment.
This zero point adjustment (calibration) of the pressure gage output is conventionally performed by an operator by manually operating a volume control so that the meter value indicates the 0 point.
In order to constantly adjust an error of the pressure gage in this manner, volume control adjustment of the pressure gage must be frequently performed manually, leading to a cumbersome operation. If the operator has forgotten to perform the 0 point adjustment, the interior of the vacuum chamber cannot be set in an appropriate vacuum state. When processing is to be performed in this chamber, an appropriate processing condition cannot be set. In a worst case, a pump and the like may overrun and thus cause an accident.